R-MATRIX FLOQUET THEORY OF MULTIPHOTON PROCESSES .3. MULTIPHOTON IONIZATION OF ATOMIC-HYDROGEN

Using the recently proposed R-matrix-Floquet theory we have analysed t he multiphoton ionization of atomic hydrogen from the ground state and the metastable 2s state in an intense, linearly polarized and monochr omatic laser field. Results are presented for total ionization rates, branching ratios into photon absorption channels (including ATI, above threshold ionization) and angular distributions, for several frequenc ies and a range of laser intensities. We also discuss the limits of lo west order perturbation theory and we study high-frequency stabilizati on at high intensities.